1. Field of the Invention
The present invention relates to an improvement of a high temperature/high pressure vessel used for an HIP (hot isostatic pressing) apparatus and more particularly to a high temperature/high pressure vessel with piano wire wound under tension round an outer periphery of a cylindrical body of the vessel.
2. Description of the Related Art
For pressure sintering of various powdery materials such as powdered metals and ceramics, for removing internal defects of cast products and sintered products, and for diffusion bonding, an HIP apparatus which utilizes a synergistic effect of a high isotropic pressure and a high temperature within a high pressure vessel is adopted in various industrial fields. The HIP apparatus is composed of a high temperature/high pressure vessel (with a heat insulating layer and a heater disposed in the interior thereof) into which a high pressure gas is sealed, an upper lid and a lower lid for closing upper and lower openings, respectively, of the vessel, and a press frame which bears an axial force acting on the upper and lower lids. As known examples of a high temperature/high pressure vessel used in such an HIP apparatus and with a refrigerant flow path formed in a cylindrical body thereof there are mentioned those disclosed in U.S. Pat. No. 3,900,189 (prior art 1) and U.S. Pat. No. 4,968,009 (prior art 2).
From the standpoint of cooling effect, the thinner the cylindrical body, the better. However, in point of strength, it is impossible to thin the cylindrical body beyond a certain level. Therefore, in the prior art 1, particularly in the case of a large-sized high temperature/high pressure vessel, it is difficult to effectively cool portions where vessel packings are disposed. As a result of the temperature of the vessel packings becoming high, the life thereof becomes short, thus causing an increase of running cost. Moreover, if the prior art 1 is of a construction wherein piano wire is wet with cooling water, the piano wire rusts, causing breaking of the wire; besides, a fatigue life of the piano wire becomes shorter. In case of a thin plate being interposed between a rod-like spacer and piano wire, the thin plate undergoes shrinkage deformation due to winding of the piano wire and there is a fear that the sealing function of a seal which prevents the permeation of cooling water may be lost.
In the prior art 2, a cooling jacket is mounted in the interior of a high pressure vessel, so that the size of a heater installed within the same vessel becomes smaller and so does the size of a workpiece. In other words, it is necessary to increase the size of the high pressure vessel, which causes an increase of cost and is therefore not desirable from the economic point of view.